Use ESM

Author: wooorm

.gitignore

@@ -1,6 +1,5 @@
 .DS_Store
 *.log
-.nyc_output/
 coverage/
 node_modules/
 yarn.lock

.prettierignore

@@ -1,3 +1,2 @@
 coverage/
-*.json
 *.md

index.js

@@ -1,11 +1,7 @@
-'use strict'
+import buffer from 'is-buffer'
+import {load} from 'js-yaml'
 
-var buffer = require('is-buffer')
-var yamlParse = require('js-yaml').load
-
-module.exports = matter
-
-function matter(file, options) {
+export function matter(file, options) {
   var settings = options || {}
   var strip = settings.strip
   var yamlOptions = settings.yaml || {}
@@ -15,14 +11,14 @@ function matter(file, options) {
   )
 
   if (match) {
-    file.data.matter = yamlParse(
+    file.data.matter = load(
       match[1],
       Object.assign({}, yamlOptions, {filename: file.path})
     )
 
     if (strip) {
       doc = doc.slice(match[0].length)
-      file.contents = buffer(file.contents) ? Buffer.from(doc) : doc
+      file.value = buffer(file.value) ? Buffer.from(doc) : doc
     }
   } else {
     file.data.matter = {}

package.json

@@ -20,44 +20,38 @@
     "type": "opencollective",
     "url": "https://opencollective.com/unified"
   },
-  "types": "types/index.d.ts",
   "author": "Titus Wormer <[email protected]> (https://wooorm.com)",
   "contributors": [
     "Titus Wormer <[email protected]> (https://wooorm.com)"
   ],
+  "sideEffects": false,
+  "type": "module",
   "main": "index.js",
+  "types": "types/index.d.ts",
   "files": [
-    "index.js",
-    "types/index.d.ts"
+    "types/index.d.ts",
+    "index.js"
   ],
   "dependencies": {
     "is-buffer": "^2.0.0",
     "js-yaml": "^4.0.0"
   },
   "devDependencies": {
     "@types/js-yaml": "^4.0.0",
-    "dtslint": "^4.0.0",
-    "nyc": "^15.0.0",
+    "c8": "^7.0.0",
     "prettier": "^2.0.0",
     "remark-cli": "^9.0.0",
     "remark-preset-wooorm": "^8.0.0",
     "tape": "^5.0.0",
-    "to-vfile": "^6.0.0",
-    "vfile": "^4.0.0",
-    "xo": "^0.38.0"
+    "to-vfile": "^7.0.0",
+    "vfile": "^5.0.0",
+    "xo": "^0.39.0"
   },
   "scripts": {
     "format": "remark . -qfo && prettier . -w --loglevel warn && xo --fix",
-    "test-api": "node test",
-    "test-coverage": "nyc --reporter lcov tape test.js",
-    "test-types": "dtslint types",
-    "test": "npm run format && npm run test-coverage && npm run test-types"
-  },
-  "nyc": {
-    "check-coverage": true,
-    "lines": 100,
-    "functions": 100,
-    "branches": 100
+    "test-api": "node test.js",
+    "test-coverage": "c8 --check-coverage --branches 100 --functions 100 --lines 100 --statements 100 --reporter lcov node test.js",
+    "test": "npm run format && npm run test-coverage"
   },
   "prettier": {
     "tabWidth": 2,
@@ -69,10 +63,9 @@
   },
   "xo": {
     "prettier": true,
-    "esnext": false,
     "rules": {
-      "guard-for-in": "off",
-      "unicorn/prefer-includes": "off"
+      "no-var": "off",
+      "prefer-arrow-callback": "off"
     },
     "ignores": [
       "types/"

readme.md

@@ -12,6 +12,9 @@ Parse the YAML front matter in a [`vfile`][vfile].
 
 ## Install
 
+This package is [ESM only](https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c):
+Node 12+ is needed to use it and it must be `import`ed instead of `require`d.
+
 [npm][]:
 
 ```sh
@@ -32,8 +35,8 @@ title: Hello, world!
 And our script, `example.js`, looks like so:
 
 ```js
-var vfile = require('to-vfile')
-var matter = require('vfile-matter')
+import {toVFile as vfile} from 'to-vfile'
+import {matter} from 'vfile-matter'
 
 var file = vfile.readSync('example.html')
 
@@ -55,6 +58,9 @@ Now, running our script (`node example`) yields:
 
 ## API
 
+This package exports the following identifiers: `matter`.
+There is no default export.
+
 ### `matter(file[, options])`
 
 Parse the YAML front matter in a [`vfile`][vfile], and add it as

test.js

@@ -1,17 +1,15 @@
-'use strict'
+import test from 'tape'
+import buffer from 'is-buffer'
+import {CORE_SCHEMA} from 'js-yaml'
+import {toVFile as vfile} from 'to-vfile'
+import {matter} from './index.js'
 
-var test = require('tape')
-var buffer = require('is-buffer')
-var vfile = require('to-vfile')
-var matter = require('.')
-var CORE_SCHEMA = require('js-yaml').CORE_SCHEMA
-
-var yaml = '---\nkey: value\nlist:\n  - 1\n  - 2\n---'
+var someYaml = '---\nkey: value\nlist:\n  - 1\n  - 2\n---'
 var doc = 'Here is a document\nMore of the document\nOther lines\n'
-var both = yaml + '\n' + doc
+var both = someYaml + '\n' + doc
 
 test('vfile-matter', function (t) {
-  var file = vfile({contents: both})
+  var file = vfile({value: both})
 
   t.equal(matter(file), file, 'should return the given file')
 
@@ -21,25 +19,25 @@ test('vfile-matter', function (t) {
     'should add data'
   )
 
-  file = matter(vfile({contents: doc}))
+  file = matter(vfile({value: doc}))
   t.deepEqual(file.data, {matter: {}}, 'should support no matter')
 
-  file = matter(vfile({contents: both}), {strip: true})
+  file = matter(vfile({value: both}), {strip: true})
   t.deepEqual(String(file), doc, 'should strip matter')
 
-  file = matter(vfile({contents: yaml}), {strip: true})
+  file = matter(vfile({value: someYaml}), {strip: true})
   t.deepEqual(String(file), '', 'should strip matter completely')
 
-  file = matter(vfile({contents: doc}), {strip: true})
+  file = matter(vfile({value: doc}), {strip: true})
   t.deepEqual(String(file), doc, 'should support no matter w/ strip')
 
-  file = matter(vfile({contents: Buffer.from(both)}), {strip: true})
-  t.ok(buffer(file.contents), 'should supporting buffers')
+  file = matter(vfile({value: Buffer.from(both)}), {strip: true})
+  t.ok(buffer(file.value), 'should supporting buffers')
 
   file = matter(vfile(), {strip: true})
-  t.ok(file.contents === undefined, 'should supporting empties')
+  t.ok(file.value === undefined, 'should supporting empties')
 
-  file = matter(vfile({contents: '---\ndate: 2021-01-01\n---\n'}), {
+  file = matter(vfile({value: '---\ndate: 2021-01-01\n---\n'}), {
     yaml: {schema: CORE_SCHEMA}
   })
   t.deepEqual(